Protected Attributes

Protect attributes from mass-assignment in Active Record models.

This plugin adds the class methods attr_accessible and attr_protected to your models to be able to declare white or black lists of attributes.

Note: This plugin will be officially supported until the release of Rails 5.0.

Installation

Add this line to your application's Gemfile:

gem 'protected_attributes'

And then execute:

bundle install

Usage

Mass assignment security provides an interface for protecting attributes from end-user injection. This plugin provides two class methods in Active Record classes to control access to their attributes. The attr_protected method takes a list of attributes that will be ignored in mass-assignment.

For example:

attr_protected :admin

attr_protected also optionally takes a role option using :as which allows you to define multiple mass-assignment groupings. If no role is defined then attributes will be added to the :default role.

attr_protected :last_login, :as => :admin

A much better way, because it follows the whitelist-principle, is the attr_accessible method. It is the exact opposite of attr_protected, because it takes a list of attributes that will be mass-assigned if present. Any other attributes will be ignored. This way you won’t forget to protect attributes when adding new ones in the course of development. Here is an example:

attr_accessible :name
attr_accessible :name, :is_admin, :as => :admin

If you want to set a protected attribute, you will to have to assign it individually:

params[:user] # => {:name => "owned", :is_admin => true}
@user = User.new(params[:user])
@user.is_admin # => false, not mass-assigned
@user.is_admin = true
@user.is_admin # => true

When assigning attributes in Active Record using attributes= the :default role will be used. To assign attributes using different roles you should use assign_attributes which accepts an optional :as options parameter. If no :as option is provided then the :default role will be used.

You can also bypass mass-assignment security by using the :without_protection option. Here is an example:

@user = User.new

@user.assign_attributes(:name => 'Josh', :is_admin => true)
@user.name # => Josh
@user.is_admin # => false

@user.assign_attributes({ :name => 'Josh', :is_admin => true }, :as => :admin)
@user.name # => Josh
@user.is_admin # => true

@user.assign_attributes({ :name => 'Josh', :is_admin => true }, :without_protection => true)
@user.name # => Josh
@user.is_admin # => true

In a similar way, new, create, create!, update_attributes and update_attributes! methods all respect mass-assignment security and accept either :as or :without_protection options. For example:

@user = User.new({ :name => 'Sebastian', :is_admin => true }, :as => :admin)
@user.name # => Sebastian
@user.is_admin # => true

@user = User.create({ :name => 'Sebastian', :is_admin => true }, :without_protection => true)
@user.name # => Sebastian
@user.is_admin # => true

By default the gem will create an empty whitelist of attributes available for mass-assignment for all models in your app.

As such, your models will need to explicitly whitelist or blacklist accessible parameters by using an attr_accessible or attr_protected declaration. This technique is best applied at the start of a new project. However, for an existing project with a thorough set of functional tests, it should be straightforward and relatively quick to use this application config option; run your tests, and expose each attribute (via attr_accessible or attr_protected), as dictated by your failing test.

This option can be turned off using a configuration option:

config.active_record.whitelist_attributes = false

For more complex permissions, mass-assignment security may be handled outside the model by extending a non-Active Record class, such as a controller, with this behavior.

For example, a logged-in user may need to assign additional attributes depending on their role:

class AccountsController < ApplicationController
  include ActiveModel::MassAssignmentSecurity

  attr_accessible :first_name, :last_name
  attr_accessible :first_name, :last_name, :plan_id, :as => :admin

  def update
    ...
    @account.update_attributes(account_params)
    ...
  end

  protected

  def account_params
    role = admin ? :admin : :default
    sanitize_for_mass_assignment(params[:account], role)
  end
end

Errors

By default, attributes in the params hash which are not allowed to be updated are just ignored. If you prefer an exception to be raised configure:

config.active_record.mass_assignment_sanitizer = :strict

Any protected attributes violation raises ActiveModel::MassAssignmentSecurity::Error then.

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request